The silicon at the center is combined with two different functional groups: primarily, the organofunctional group "X" which plays the most important role in the adhesion promotion in terms of adjusting the polarity or reactivity of the NFC and secondly, the functional alkoxy groups "OR". The bonding of the alkoxysilanes to the NFC takes place by hydrolysis of the alkoxy-group(s), followed by the condensation of the organofunctional silicon- backbone with the hydroxyl-groups on the surface of the nanofibrils: